Dihydronepetalactone (DHN) has been shown to be an effective insect repellent, as discussed in U.S. Ser. No. 05/112,166. Dihydronepetalactone can be produced by hydrogenating nepetalactone, a component of the essential oil from the catmint plant, Nepeta cataria (herein referred to as catmint oil). Catmint oil can be purified from plants of the N. cataria by various isolation processes including steam distillation [Regnier, F. E. et al, Phytochemistry (1967) 6:1281-1289], organic solvent extraction, microwave-assisted organic solvent extraction, supercritical fluid extraction, mechanical extraction and enfleurage (initial cold extraction into fats followed by organic solvent extraction). The catmint oil so obtained can be used in the crude form to produce DHN, however the hydrogenation reaction can be adversely affected by undesirable components contaminating the crude catmint oil.
Nepetalactone has been purified from catmint oil by crystallization [Regnier, F. E. et al, Phytochemistry (1967) 6:1271-1280], however crystallization is expensive, and on the potential scale required for commercialization, it is uneconomical. Therefore, it would be highly desirable to produce a catmint oil with improved properties, such that high yields of the insect repellent DHN may be produced.